/Engine/Source/Editor/GraphEditor/Public/BlueprintConnectionDrawingPolicy.h
This function recursively searches for any pins feeding the OutputPin (or the OutputPin itself); it looks for a pin on a non-reroute node (one that is listed in NodeExecutionList).
Null if OutputPin did not cause the invocation of the node in question, otherwise a valid time pair denoting when the node was executed.
[FTimePair](API\Editor\GraphEditor\FKismetConnectionDrawingPolicy\FTimePair) const * BackTraceExecPath ( [UEdGraphPin](API\Runtime\Engine\EdGraph\UEdGraphPin) const *const OutputPin, [FExecPairingMap](API\Editor\GraphEditor\FKismetConnectionDrawingPolicy\FExecPairingMap) const *const NodeExecutionList )